JM 3-15.170
The Attorney General and the Deputy Attorney General, as delegated by the Attorney General, may, in appropriate cases, authorize the Director of the United States Marshals Service to deputize United States Attorney personnel on an individual basis as Special Deputy United States Marshals for the limited purpose of carrying firearms for self protection. Such deputations will enable them to possess and carry firearms without violating local, state, and federal laws which may restrict the possession or carrying of firearms. Such deputations expressly exclude law enforcement powers such as the power to arrest for violations of federal law and court-related duties of United States Marshals.
[updated February 2018]